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APM: Preliminary test results

Posted by mhamilton on June 20, 2000 at 09:13:41:
While my time was limited and my tests not complete,
I built the APM using several different ferrite clamps from
the FairRite company. (I have data on these clamps if anyone
wants to see the scanned-in data sheet).
Using 18 AWG zip-cord I wrapped 5 to 6 wraps on each device.
Then I set up my Network Analyzer and calibrated it.
(HP 4195A) and tried to measure both the Characteristic
Impedance vs. frequency and the Reflection transfer function of the
network.
Now mind you, these ferrites (and all EMI ferrites) don't really
get interesting until way up in the 100's of Megahertz (this
is where the impedance, reactance, and resistance peak). But
my assumption is that any audio affects, and any affects on
motors (fans etc) is are gonna be in the less than 1 MHz region.
First I did some wide sweeps out to 1 MHz. As might be expected
there was really no difference in a stright 2 foot wire and a
two foot wire wrapped around a ferrite. Impedance was about 50
ohms +/- 10 ohms out to about 1 MHz then there was some crazy
reflections due to the open circuit.
Given the observations that this tweak needs a few minutes to work
I put the analyzer on a very slow sweep (maybe not slow enough)
and 100 Hz Resolution BW. Also, I had to limit the sweep (for time).
So I looked at 10 Hz to 1000 Hz. I tried various ferrites. Again
no observable significant change in impedance or reflection
characteristics.
So I took the ferrites home and did a quick test vs. the refrigerator.
Plugged in to each of the outlets in the kitchen. None seem to affect
the sound of the refrigerator nor the hum from the flourescent lights.
More testing later.
Thoughts.
IF this thing was to act as a Power Factor Corrector, a soft
iron core like those used in crossovers would have much more
energy storage at low-freq. A lot of energy storage is required
to correct the phase shift caused by an inductive motor like
those in an A/C or washing machine or refrigerator.
( I think, someone correct me if I'm wrong about this).
Another thought. Might a better tweak be to terminate all of the
unused outlets in your house with a bypass capacitor??? Maybe
using UL rated Y-CAPs you could shunt H and N to GND. This would
help damp higher frequency reflections on all the stubs throughout
the house. No doubt when a motor or a switching power supply
or a triac controlled dimmer is turned on anywhere in the house
is causes long-lasting ringing noise throughout the network - even
back to the panel to get and onto your (my) dedicated circuits.
This would reduce differential noise and not common-mode noise.
Of course I would prefer to stop noise at the source. A filter
on every motor, triac, computer, etc.
What a great way to waste time and avoid work.